1. Field of the Invention
The present invention relates to variable-advance motion generating mechanisms, and more particularly to punched card controlled pattern generating mechanism, such as are used in conjunction with embroidering machines, for example.
2. Description of the Prior Art
Automatic embroidering machines may be of the single-needle type or of the multi-needle type. A machine of the latter designation has a number of embroidering stations, each with an embroidering needle executing a continuous stitching motion. The embroidery pattern is created by moving the fabric under the needle. For this to happen, the embroidery frame must execute a lateral movement, in order to create the sewing of the embroidery stitches, and a fabric advancing movement, in order to develop the embroidery design.
The emrbroidery frame movements which are required for the production of even simple embroidery designs are so complex and require so many different movement increments that the automatic generation of these movements virtually always requires the use of an information carrier from which the pattern instructions are read and automatically converted into corresponding embroidery frame movements. Probably the oldest type of information carrier, and still in many cases the best suited one, are punched cards or a punched tape, frequently referred to as jacquard cards or jacquard tapes.
One such punched card embroidery pattern control mechanism is disclosed in the German Pat. No. 429,395. The mechanism suggested in this prior art disclosure is intended to produce a sequence of embroidery frame movements whose magnitude is randomly adjustable to any integer between 1 and 40. To accomplish this, the prior art mechanism features a punched tape reading mechanism which translates the absence of a hole in the tape into a control motion of one of a pair of cam slides which interacts with a gear-type analog computer to produce either a positive, or a negative, or zero movement input. Subsequent pairs of cam slides produce movement inputs of a different magnitudes which are combined by the differential gear type computer, so as to selectively produce output magnitudes which may vary between 1 unit and 40 units. A similar device may be used to produce the second embroidery frame motion component.
The described prior art mechanism has enjoyed considerable commercial success. One of its shortcomings, however, relates to the fact that it requires a comparatively heavy punched tape, since the latter has to be strong enough to withstand the forces which are necessary to move the cam slides and, by way of the latter, the levers and gears of the differential gear computer mechanism. Another shortcoming of this mechanism is its comparatively slow rate of operation, due to the limitations on its reading speed which, if increased, correspondingly increases the risk of damage to the punched tape, due to the mass inertia of the parts which are being directly driven by the punched tape.